In some conventional lighting systems, the control variables for lighting relate directly to an individual luminaire's output (such as intensity or color temperature of light emitted by the luminaire). In these conventional systems, as the number of luminaires in a room increases, the number of control variables needed becomes too great for practical use. For instance, a conventional lighting system with ten solid-state luminaires, each with three color channels (RGB), may have at least 30 control variables. This large number of control variables may—in these conventional systems—make the control system unacceptably complex for the user.
In some other conventional systems, preprogrammed lighting scenes are employed to improve usability. For instance, in some conventional systems, the user is allowed a choice of only a small number of lighting scenes, where the overall brightness of each luminaire, and the color or color temperature for each luminaire, are pre-computed for each lighting scene. This conventional approach (with a small number of precomputed lighting scenes) reduces complexity of control for the user. However, it restricts the user to only a small fraction of lighting configurations, out of the vastly larger number of lighting configurations which could be realized with a given set of luminaires in the room.
In some recent lighting control systems, a user controls lighting in a room by employing what we loosely call “perceptual control dimensions.” In these recent systems, each perceptual control dimension corresponds to how humans would perceive lighting in a room as being conducive to a particular mental state or to a particular type of human activity. For instance, in a recent system, three perceptual control dimensions are “Casual”, “Presentation” and “Visually Demanding”, where: (a) different positions along the “Casual” axis indicate the extent to which a human would perceive lighting in the room as being conducive to casual social interaction or relaxing; (b) different positions along the “Presentation” control axis indicate the extent to which a human would perceive lighting in a room as being conducive to making a visual presentation (such as with PowerPoint® slides); and (c) different positions along the “Visually Demanding” control axis indicate the extent to which a human would perceive lighting in a room as being conducive to a visual demanding task such as studying. In this example, a user may—by selecting coordinates along the Casual, Presentation and Visually Demanding axes—adjust the overall brightness and RGB intensities of each luminaire in a room. Thus, in this example, there are only three control dimensions, yet these three dimensions afford the user the ability to select any of a very large number of lighting combinations. Furthermore, in this example, these three perceptual dimensions correspond to how a user perceives lighting in the room, rather than corresponding to physical output settings of individual luminaires or to only a few pre-computed lighting configurations.
In these recent systems, perceptual control dimensions may be determined from user ratings. For instance, human users may view a room under different lighting scenes and then fill out a survey regarding their perception of the different lighting scenes. A dimensionality reduction algorithm may be employed to produce a low-dimensional representation of these user ratings. For instance: (a) PCA (principal component analysis) may be employed to reduce this user data to principal components where each component has the highest variance possible under the constraint that it is orthogonal to the preceding component; and (b) the first two or three principal components may be selected as the perceptual control dimensions. For instance, the first three principal components may be the “Casual”, “Presentation” and “Visually Demanding” control dimensions described above.
A problem with these recent systems (which employ perceptual control dimensions) is that it may be too expensive and time-consuming to gather user ratings for a large number of lighting scenes each time that the lighting control system is deployed in a new room. A related problem with these recent systems is that it is difficult to generalize from one room to the next, without repeating the entire user rating process for the new room.